This invention relates, in general, to input/output processing, and in particular, to measuring resource usage related to input/output processing.
In large computing systems, a measurement facility is often available that provides information about traffic through the input/output (I/O) infrastructure. Such information is useful for tuning program performance, load balancing, and for billing users based on resource usage.
As one particular example, in System z® machines offered by International Business Machines Corporation, utilities are provided to obtain information about traffic flowing through the I/O infrastructure, which is referred to as the channel subsystem. The channel subsystem provides a consistent interface for channel access across channel types and various I/O subsystem transports. This interface, referred to as the Start Subchannel Call instruction, is executed by firmware on behalf of the user. The firmware hides details of the physical channel from the user and is provided utilities, such as a measurement utility, to track resource usage.
With other I/O infrastructures, however, the details of the physical channel are exposed to the user and facilities provided by those infrastructures that hide the details are not available.